The present invention relates to microfluidic devices, and more particularly, to a method of moving fluid within or out of a microfluidic device.
Methods of making a homologous series of compounds, or the testing of new potential drug compounds comprising a series of light compounds, has been a slow process because each member of a series or each potential drug must be made individually and tested individually. For example, a plurality of potential drug compounds that differ perhaps only by a single amino acid or nucleotide base, or a different sequence of amino acids or nucleotides are tested by an agent to determine their potential for being suitable drug candidates.
The processes described above have been improved by microfluidic chips, which are able to separate materials in a micro channel and move the materials through the micro channel. Moving the materials through micro channels is possible by use of various electro-kinetic processes such as electrophoresis or electro-osmosis. Fluids may be propelled through various small channels by the electro-osmotic forces. An electro-osmotic force is built up in the channel via surface charge buildup and by means of an external electric field that can repel fluid and cause flow.
In fluid delivery in microfluidic structures, several layers comprise the device. Channels often extend between the various layers. A capillary break structure is used in place of a valve downstream of an electrohydrodynamic pump in a channel. The capillary break is a location where the small channel ends abruptly as the entrance to a larger space. Capillary forces pull the fluid up to the end of the small cross-section channel but not beyond. This stops the fluid flow until additional pressure is provided. Prior to pushing fluid beyond the capillary break, a gap or discontinuity occurs in the fluid path immediately downstream of the capillary break. This prevents cross-contamination from other fluid paths.
In some instances, an electrohydrodynamic pump generates a relatively low pressure and may not be able to overcome the capillary break without an additional pressure applied. Also, size, uniformity, and other fabrication tolerances cause variances in the effectiveness of electrohydrodynamic pumps. Also, the microfluidic chip is preferably designed to be used with several different types of fluid. The variation of fluid properties, such as composition and temperature, also affect the ability of an electrohydrodynamic pump to overcome the capillary break.
It would, therefore, be desirable to enable a capillary break to be overcome for various fabrication tolerances and fluids used within the microfluidic device. It would also be desirable to sense the proper operation of a capillary break.
It is, therefore, one object of the invention to provide an improved fluid delivery mechanism to an array of reaction wells.
It is a further object of the invention to reliably overcome a capillary break in spite of manufacturing tolerances.
In one aspect of the invention, a microfluidic device has a layer that has a capillary break formed by a capillary sluice. The capillary sluice has a lower surface and an upper surface. An input channel is coupled to the capillary break. A first electrode is disposed proximate the lower surface. The first electrode is coupled to the voltage source. A second electrode is spaced a first predetermined distance from the first electrode coupled to the voltage source. A third electrode is spaced apart from the second electrode and positioned within the input channel from the first electrode coupled to the voltage source.
One advantage of the invention is that the controller and the software therein may be adjusted to control the operation of the microfluidic device.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.